JP2546042Y2 - Exhaust brake device for diesel engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a diesel engine having an exhaust gas purification device such as a particulate trapper or a catalytic converter in an exhaust system and an exhaust brake upstream of the device.

[Conventional technology]

Exhaust gas purifiers such as particulate trappers and catalytic converters are installed in the exhaust system of diesel engines to remove harmful components in exhaust gas. On the other hand, in a diesel engine, a normally open butterfly valve which operates as an exhaust brake in an exhaust system is provided, and when the accelerator pedal is released, this valve is closed to perform braking. An example of a diesel engine having a particulate trapper and an exhaust brake is Japanese Utility Model Laid-Open No. 62-184126.

[Problems to be solved by the invention]

In a diesel engine having both a particulate trapper and an exhaust brake, the temperature of the particulates becomes abnormally high immediately after the release of the exhaust brake, and there is a possibility of melting of the particulates. That is, during the operation of the exhaust brake, the exhaust gas is partially pushed back into the combustion chamber, so that a so-called internal exhaust gas recirculation (EGR) is applied, and the combustion chamber is in an oxygen-deficient state.
Then, when the exhaust brake is released and the vehicle shifts to acceleration, a normal amount of fuel is injected, so that there is a shortage of air, and most of the fuel becomes unburned gas and is discharged to the exhaust pipe. This unburned gas rapidly reacts with the catalyst carried on the particulate trapper (or catalytic converter), and reaches a considerably high temperature, which may lead to melting.

Therefore, in Japanese Utility Model Laid-Open Publication No. 3-35214, a bypass passage bypassing the particulate trapper is connected to the exhaust pipe, and a switching valve is provided between the exhaust brake and the particulate trapper. The exhaust valve is positioned to stop the flow of exhaust gas to the bypass passage when the exhaust brake is released. When the exhaust brake is released, the switching valve is positioned to form a flow to the bypass passage. Therefore, the exhaust gas can escape to the bypass passage when the exhaust brake is operated, and the catalyst can be prevented from being melted.

[Problems to be solved by the invention]

In the configuration disclosed in Japanese Utility Model Laid-Open No. 3-35214, a switching valve is provided in addition to the exhaust brake, and the switching valve is installed between the exhaust brake and the particulate trapper. In this case, a switching valve and a drive mechanism for the switching valve are additionally required in a normal exhaust brake device.

This invention aims to avoid the risk of melting when the exhaust brake is released without installing a switching valve.

[Means for solving the problem]

According to this invention, an exhaust gas purifying device such as a particulate trapper or a catalytic converter is provided in an exhaust system, and an exhaust brake device comprising an on-off valve for opening and closing the flow of exhaust gas in the exhaust system is provided. Is located upstream of the exhaust gas purifying device, the on-off valve closes the exhaust system when the exhaust brake device is operating, opens the exhaust system when the exhaust brake device is released, and opens when the exhaust brake device is released. In a diesel engine in which a bypass passage that forms an exhaust gas flow bypassing an exhaust gas purification device is connected to an exhaust system, the on-off valve is provided in an exhaust system in which an upstream end of the bypass passage is opened when an exhaust brake device operates. It is located upstream from the portion, and it is assumed that the flow of exhaust gas to the bypass passage is prohibited when the exhaust brake device is operated by only the open / close valve. Diesel engine is provided, characterized in that to permit the flow of exhaust gas to the bypass passage during release of the exhaust brake device.

[Action]

When the exhaust brake device operates, the on-off valve is located upstream of a portion of the exhaust system in which the upstream end of the bypass passage is opened when the exhaust brake device operates. This prohibits the flow of exhaust gas to the bypass passage.

The release of the exhaust brake device opens the on-off valve, and allows the flow of exhaust gas to the bypass passage.

〔Example〕

In FIG. 1, reference numeral 10 denotes an engine body, and an intake pipe 1
2. The exhaust pipe 14 is connected. The exhaust pipe 14 is connected to an exhaust brake device 16 and a particulate trapper 18 (or an exhaust gas purifying device such as a catalytic converter). The exhaust brake device 16 includes a main body 20 through which exhaust gas flows, and an on-off valve.
22 and a negative pressure actuator 24 for driving the on-off valve 22. One end of a lever 26 is fixed to the valve shaft of the on-off valve 22,
The other end of the lever 26 is connected to a diaphragm 30 of the actuator 24 via a rod 28. The spring 32 urges the diaphragm 30 downward, and this downward movement is
And the on-off valve 22 is normally in the fully open position in FIG. The lower diaphragm chamber 34 of the diaphragm 30 is open to the atmosphere, the upper diaphragm chamber 36 is connected to an electromagnetic three-way switching valve 40, and when the electromagnetic three-way switching valve 40 is in the OFF state, the diaphragm chamber 36 passes through the throttle 41. Air filter
Connected to 42, and in the ON state, the negative pressure pump 48 of the diesel engine
Connect to

In this embodiment, the operation of the exhaust brake is performed when the exhaust brake operation switch 50 is turned on and the accelerator pedal 52 is released. Contact 54 of accelerator pedal switch 54
-1 is in series with the exhaust brake operation switch 50,
When both switches 50 and 54-1 are both ON, transistor 56
Energizes the operating coil 40-1 of the electromagnetic three-way switching valve 40 to operate the exhaust brake.

Numeral 60 is a bypass passage and a particulate trapper.
One end of the bypass passage 60 is provided so as to bypass the 18.
60-1 is connected to the main body 20 upstream of the particulate trapper 18, and the other end is connected downstream of the particulate trapper 18. FIG. 2 shows a state in which the exhaust brake device is in the operating state, and the on-off valve 22 is in the fully closed position. Body 20
A stopper projection 20-1 is formed on the inner periphery of the valve 20. The on-off valve 22 takes this fully closed position by contacting the projection 20-1.
One end 60-1 of the bypass passage 60 is opened slightly downstream of the on-off valve 22 at the fully closed position in FIG.

When the exhaust brake setting switch 50 is OFF or the switch 50 is ON, the accelerator pedal switch 54-1 is turned off.
In the case of F (when the accelerator pedal 52 is depressed), the transistor 56 is OFF, the electromagnetic three-way switching valve 40 is OFF, and the atmospheric pressure is introduced from the air filter 42 into the diaphragm chamber 36, so that the spring 32 As a result, the diaphragm 30 is driven downward in the figure, and the on-off valve 22 assumes the fully open position in FIG. Therefore, the exhaust brake operation cannot be obtained.

When the accelerator pedal 52 is released with the exhaust brake setting switch 50 turned on, the switch 54-1 is turned on, the transistor 56 is turned on, and the electromagnetic three-way switching valve 40 is energized,
A negative pressure is introduced into the diaphragm chamber 36. Therefore, the diaphragm 30 rises against the spring 32, and this rising movement is transmitted to the on-off valve 22 via the rod 28 and the lever 26,
As shown in FIG. 2, the on-off valve 22 assumes a fully closed position in contact with the stopper 20-1. Therefore, the flow of the exhaust gas is locked, and the engine is greatly braked. At this time, the on-off valve
22 is an upstream end 60-1 of the bypass passage 60 as shown by a solid line.
Is located upstream from the part of the exhaust system where the
Exhaust gas flow to the bypass passage is prohibited.

When the accelerator pedal 52 is depressed, the switch 54-1 is turned off and the transistor 56 is turned off.
0 is turned off, the atmospheric pressure from the air filter 42 is introduced into the diaphragm chamber 36, the spring 32 moves the diaphragm 30 down, and the open / close valve 22 is opened by rotating clockwise. When the on-off valve 22 is opened from the fully closed state, first, as shown by the imaginary line 1 in FIG.
A part of the exhaust gas on the upstream side that has opened is introduced into the bypass passage 60 as shown by the arrow F, and the amount of the exhaust gas toward the particulate trapper 18 is reduced accordingly. Trapper
Since the amount of exhaust gas to 18 is suppressed, the temperature can be appropriately maintained. That is, due to the internal exhaust gas recirculation (EGR) effect as described above, the exhaust gas upstream of the on-off valve 22 immediately after the release of the exhaust brake operation is temporarily oxygen deficient.
Exhaust gas is trapped in the trapper
If sent to 18, there is a risk that it will react rapidly and become hot, but at least part of the exhaust gas will escape to the bypass passage 60 immediately after the exhaust brake is released and will not go to the trapper 18, so the reaction at the trapper 18 will be stopped. It can be suppressed appropriately.

The opening speed of the on-off valve 22 of the exhaust brake 24 is appropriately set so that the unburned fuel temporarily formed on the upstream side during the exhaust brake allows excess exhaust gas to bypass the bypass passage 60. In this embodiment, the provision of the throttle 41 controls the introduction speed of the atmospheric pressure into the diaphragm chamber 36, so that an appropriate opening speed of the on-off valve can be obtained.

The projection 20-1 separates the flow of exhaust gas along the inner peripheral wall,
The exhaust brake is released and the on-off valve 22 serves to guide the flow of exhaust gas when the valve is fully opened to the particulate trapper 18.

The size of the bypass passage 60 is not required to be large because the bypass passage 60 is only for coping with a temporary lack of air and excess fuel immediately after the release of the exhaust brake. Therefore, when the on-off valve 22 is fully opened with the exhaust brake released, the amount of exhaust gas flowing toward the bypass passage 60 can be made small enough to be ignored.

〔effect〕

According to this invention, the on-off valve is located upstream of a portion of the exhaust system in which the upstream end of the bypass passage is opened when the exhaust brake device operates, and only the on-off valve is used to operate the exhaust brake device. Exhaust gas flow to the bypass passage is inhibited during operation, and exhaust gas flow to the bypass passage is allowed when the exhaust brake device is released. Therefore, the switching valve and its driving device as in the related art become unnecessary, and the simplification of the configuration and the reduction in cost can be realized.

[Brief description of the drawings]

FIG. 1 is an overall schematic view of the present invention. FIG. 2 is a detailed sectional view of the exhaust brake device. 10 ... internal combustion engine, 12 ... intake pipe, 14 ... exhaust pipe, 16 ...
Exhaust brake device, 18 ... Particulate trapper (or catalytic converter), 22 ... On-off valve, 24 ... Actuator, 30 ... Diaphragm, 32 ... Spring,
36 ... Diaphragm chamber, 40 ... 3-way switching valve, 48 ... Negative pressure pump, 50 ... Exhaust brake operation control switch, 52 ...
Accelerator pedal, 54 ... Accelerator pedal switch.

Claims (1)

(57) [Scope of request for utility model registration] An exhaust system is provided with an exhaust gas purifier such as a particulate trapper or a catalytic converter, and an exhaust brake device comprising an open / close valve for opening and closing the flow of exhaust gas in the exhaust system. The on-off valve is located upstream of the exhaust gas purification device, and the on-off valve closes the exhaust system when the exhaust brake device operates, opens the exhaust system when the exhaust brake device is released, and releases the exhaust system when the exhaust brake device is released. In a diesel engine in which a bypass passage that forms a flow of exhaust gas bypassing a gas purification device is connected to an exhaust system, the on-off valve is a portion of the exhaust system in which an upstream end of the bypass passage is opened when an exhaust brake device is operated. It is located on the more upstream side, and prevents the flow of exhaust gas to the bypass passage when the exhaust brake device is operating, while only using the open / close valve. Diesel engine, characterized in that to permit the flow of exhaust gas to the bypass passage during release of the brake system.